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Old 4th Aug 2010, 11:25 am   #1
'LIVEWIRE?'
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Question Clarion/Range Rover PRC8290(PU9590C)

This '90s Car Stereo has a fault somewhere in it's switching circuit, which means that (a) approx. 300mA is drawn via the PERMANENT +12v supply, and (b) The radio is still powered when it's on/off switch is turned off, although the switch itself is working as it should. I have checked switching transistors & related components to no avail. Even with a sub-panel containing these components is un plugged(which also removes the Accessory supply)some 300mA is still being drawn via the permanent supply line-much higher than it should be. If all else fails, I'll power both the permanent and accessory lines via the ignition, as I suspect the fault may be difficult to pin down/rectify, but can anyone reading this help with a proper cure?
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Old 4th Aug 2010, 1:07 pm   #2
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Default Re: Clarion/Range Rover PRC8290(PU9590C)

When you say "powered" do you mean working with sound, or "lit up"? I'm wondering if your checking the "illumination" wire instead of the permanent live?

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Old 4th Aug 2010, 7:17 pm   #3
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Default Re: Clarion/Range Rover PRC8290(PU9590C)

The radio is powered, with the display showing 98.1Mhz U1 even with the (conventional mechanical) on/off switch in the 'Off' Position. I have checked the quiescent current drawn by the Permanent, Accessory, and dial illumination supplies seperately, with the result noted in post #1. Further checks today have not produced a solution. I even removed a diode connected between the Acc. & Permanent supply lines, although it checked out OK 'cold', because a point marked 'Acc' on the PCB still had +12v on it with the supply to the Acc line removed Didn't make any difference. Possibly the fault is in the main microprocessor. If so, the answer will be to do as I stated at the end of post #1. I don't have the service manual for this early 90s OEM fit stereo, either!
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Old 4th Aug 2010, 7:59 pm   #4
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Default Re: Clarion/Range Rover PRC8290(PU9590C)

Does the On/Off switch switch the power input or does it go to the processor. Usually, the On/Off switching is a pulse to the processor if it does not switch the power. In this case, follow the pulse through and see if you can find a break.

If it does switch the power supply, could it be as simple as the switch being faulty?

Cheers,

Steve P.
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Old 5th Aug 2010, 10:07 am   #5
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Default Re: Clarion/Range Rover PRC8290(PU9590C)

Steve, the switch works OK(reads o/c when 'off' and ca. 1 ohm when 'on'). The + 12v supply is then taken to the emitter of Q504-a 2SAxxx*, which is then turned 'on' via a transistor/resistor combination biased via the 'remote 1'(Clarion's description!)line from the master uP, but you could be right-there is probably another line to/from the uP which isn't being reset to '0V' when the set is switched off
*I don't have the radio in front of me and can't remember the type no of the device! Circuit references are from a Clarion manual for a different model with a power o/p stage built in-the PU9590C is line o/p only.
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